Continuously variable transmission for an internal combustion engine

ABSTRACT

A continuously variable transmission (“CVT”) is disclosed. The CVT includes a drive pulley adapted to connect to a crankshaft of an engine. The drive pulley has inner and outer halves with belt engagement surfaces to engage the sides of the belt. The drive pulley of the CVT also includes a slide sleeve disposed on the shaft adapted to engage an inner side of a belt. The inner and outer halves of the drive pulley are biased apart from one another by a spring. The slide sleeve engages the belt when the belt is stationary or traveling at low speeds. The driven pulley includes inner and outer halves with belt engagement surfaces. The two halves are biased into contact with one another. A connector connects the inner half to the outer half. In addition, a pneumatically-actuated driven pulley is described together with a CVT incorporating same.

This application relies on the following three provisional applicationsfor priority: (1) U.S. Provisional Patent Application Ser. No.60/229,338, entitled “FLEX Engine 610,” which was filed on Sep. 1, 2000;(2) U.S. Provisional Patent Application Ser. No. 60/263,501, entitled“FLEX Engine 610,” which was filed on Jan. 24, 2001; and (3) U.S.Provisional Patent Application Ser. No. 60/316,030, entitled“Continuously Variable Transmission for an Internal Combustion Engine,”which was filed on Aug. 31, 2001. All three applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the design and construction of anengine, in particular an internal combustion engine. More specifically,the present invention relates to the construction and design of variousaspects of a continuously variable transmission (“CVT”) for an internalcombustion engine.

2. Description of the Prior Art

The prior art includes several examples of CVT that have beencontemplated for use on a number of vehicles. For example, CVTs havebeen designed for use on recreational vehicles, such as snowmobiles andall terrain vehicles (“ATVs”). They have also been designed forautomobiles.

A continuously variable transmission is considered to be superior to atraditional geared transmission becase, unlike a traditional gearboxthat provides four or five separate gears, a CVT provides a infinitenumber of different “gears.” As a result, CVTs are much more efficientat transmitting torque from the engine to the output shaft of thetransmission.

One drawback with CVTs, however, is that they cannot operate in areverse torque transmission mode (or “RTT”). This is due to the beltedconstruction that is a fundamental aspect of CVTs.

When a transmission is operating in an RTT mode, movement of the vehiclecontaining the transmission is transferred, through the transmission, tothe engine to start the engine. This is likened to starting car with ageared transmission by rolling the car down a hill a “popping” theclutch.

Since CVTs are incorporated in recreational vehicles that can be drivenfar from a repair station, should the engine starter fail, it isdeirable to include a transmission with a RTT mode of operation. Thisneed has become more pronounced recently with the introduction of fourstroke engines (as opposed to two stroke engines) in recreationalvehicles. Four stroke engines are more difficult to start because thenumber of components that must be moved in relation to one another toset the system in motion.

SUMMARY OF THE INVENTION

In view of the foregoing, it is therefore one object of the presentinvention to provide a continuously variable transmission that canoperate in a RTT mode of operation.

Accordingly, it is one aspect of the present invention to provide adrive pulley for a CVT with a shaft adapted for operative connection tothe engine crankshaft. An inner half of the drive pulley is disposed onthe shaft, the inner half having a belt engagement surface associatedtherewith adapted to engage a first side of a belt. An outer half alsois disposed on the shaft, the outer half having a belt engagementsurface associated therewith adapted to engage a second side of a belt.A slide sleeve is disposed on the shaft adapted to engage an inner sideof a belt. In addition, a spring is provided that biases the inner halfand the outer half of the drive pulley apart from one another. The slidesleeve freely rotates with respect to the shaft when the belt is engagedthereby and the belt either is stationary or travels in a firstdirection.

It is still another aspect of the present invention to provide a drivepulley for a CVT that additionally includes at least one groove disposedon an inner surface of the slide sleeve and at least one pin extendingfrom the shaft, the pin being biased to engage the at least one groove.

One further aspect of the present invention is to provide a drive pulleyfor a CVT where the at least one groove in the slide sleeve comprisesthree grooves spirally disposed on the inner surface of the slide sleeveand the at least one pins comprises three pins, one each disposed inconnection with each groove.

Another aspect of the present invention is to provide a drive pulley fora CVT where the grooves in the slide sleeve each comprise first andsecond surfaces, the second surface being angled more steeply than thefirst surface. The first surface permits the pins to slide therefromwhen the belt engages the slide surface and the belt either isstationary or travels in the first direction. The second surface permitsthe pins to engage therewith when the belt travels in a seconddirection, opposite to the first.

Still another aspect of the present invention is to provide a drivepulley for a CVT where the slide sleeve also includes an annular flangeextending outwardly from an outer surface on one end. The annular flangeengages at least a portion of the first side of the belt when the beltengages the slide sleeve.

One further aspect of the present invention is to provide a drive pulleyfor a CVT that also includes at least one antifriction bearingjournaling the slide sleeve to the shaft.

An aspect of the present invention is to provide a drive pulley for aCVT where the outer half further comprises at least one centrifugalweight pivotally mounted thereto so that the centrifugal weight swingsoutwardly upon application of a centrifugal force, applies a pressingforce against an associated roller disposed on the outer half, andcauses the outer half belt engaging surface to move towards the innerhalf belt engaging surface, sandwiching the belt therebetween.

An additional aspect of the present invention is to provide a drivepulley for a CVT where the at least on centrifugal weight is providedwith a plurality of indentations on its outer surface to engage theroller at specific engine speeds, momentarily delaing the advancement ofthe outer half belt engagement surface toward the inner half beltengaging surface, and providing an operation comparable to a traditionalgeared transmission.

One further aspect of the present invention is to provide a drivenpulley for a CVT that includes a shaft adapted for operative connectionto an output shaft of the continuously variable transmission. An innerhalf is disposed on the shaft, the inner half having a belt engagementsurface associated therewith adapted to engage a first side of a belt.An outer half disposed on the shaft, the outer half having a beltengagement surface associated therewith adapted to engage a second sideof a belt. A spring biases the inner half and the outer half togetherwith one another. A connector rotatably couples the inner half with theouter half. The connector is disposed between the inner half and theouter half.

Another aspect of the present invention is to provide a driven pulleyfor a CVT where the connector comprises a ring having at least oneribbed portion and at least one non-ribbed portion, and the inner halfand the outer half both comprise at least one ridged section adapted toengage the at least one ribbed portion of the connector.

Also, it is an aspect of the present invention to provide a drivenpulley for a CVT having a toothed wheel fixedly connected to the shaft.A guide member operatively connects to the toothed wheel and has atleast one projection adapted to mate with at least one indentation onthe inner half.

One aspect of the present invention is to provide a driven pulley for aCVT where the at least one projection on the guide member includes afirst ramp with at least one first slope and a second ramp with at leastone second slope that is less than the at least one first slope. Thefirst ramp is adapted to engage the inner half during a normal mode ofoperation of the driven pulley and the second ramp is adapted to engagethe inner half during a reverse torque transmission mode of operation ofthe driven pulley.

A further aspect of the present invention is to provide a CVT includinga drive pulley adapted to connect to a crankshaft of an engine. Thedrive pulley includes a drive pulley inner half disposed on the shaft,the drive pulley inner half having a belt engagement surface associatedtherewith adapted to engage a first side of a belt. The drive pulleyalso includes a drive pulley outer half disposed on the shaft, the drivepulley outer half having a belt engagement surface associated therewithadapted to engage a second side of a belt. The drive pulley furtherincludes a slide sleeve disposed on the shaft adapted to engage an innerside of a belt and a spring biasing the drive pulley inner half and thedrive pulley outer half apart from one another. The slide sleeve freelyrotates with respect to the shaft when the belt is engaged thereby andthe belt either is stationary or travels in a first direction. The CVTalso includes a driven pulley adapted to connect to an output shaft ofthe continuously variable transmission. The driven pulley has a drivenpulley inner half disposed on the shaft, the driven pulley inner halfhaving a belt engagement surface associated therewith adapted to engagea first side of a belt. It also has a driven pulley outer half disposedon the shaft, the driven pulley outer half having a belt engagementsurface associated therewith adapted to engage a second side of a belt.A spring biases the driven pulley inner half and the driven pulley outerhalf together with one another. A connector rottably couples the drivenpulley inner half with the driven pulley outer half, The connector isdisposed between the driven pulley inner half and the driven pulleyouter half.

One further aspect of the present invention is to provide apneumatically-actuated driven pulley.

Another aspect of the present invention is to provide a driven pulleyfor a continuously variable transmission. The driven pulley includes ashaft adapted for operative connection to an output shaft of thecontinuously variable transmission. An inner half is rotatably disposedon the shaft, the inner half having a belt engagement surface associatedtherewith adapted to engage a first side of a belt. An outer halfrotatably disposed on the shaft, the outer half having a belt engagementsurface associated therewith adapted to engage a second side of a belt.A spring biases the inner half and the outer half together with oneanother. A chamber is disposed relative to the inner half and the outerhalf, wherein the chamber is adapted to respond to a change in gaspressure therein, which causes the inner and outer halves to clamp ontothe belt.

A further aspect of the present invention is to provide a driven pulleywhere the chamber is disposed between the inner and outer halves, andthe change in gas pressure results from the application of apredetermined vacuum to the chamber.

One additional aspect of the present invention is to provide a drivenpulley where the vacuum is supplied by an engine.

Another aspect of the present invention is to provide a driven pulleywhere the vacuum is supplied by a vacuum pump.

An aspect of the present invention also is to provide a driven pulleythat includes a pressure connector attached to the shaft, wherein thepressure connector is operatively connected to the chamber.

Still another aspect of the present invention is to provide a drivenpulley where the chamber is disposed adjacent to either the inner or theouter half, and the change in gas pressure results from the introductionof a predetermined pressure to the chamber.

Other aspects of the present invention will be made apparent from thedescription that follows and the drawings appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the various drawings that are appended hereto, like partswill be referred to by like reference numbers, in which:

FIG. 1 is a cross-sectional view of the engine of the present inventiontaken perpendicularly to the longitudinal centerline of the engine (thecenterline being defined as the line running through the center of thesingle cylinder of the engine);

FIG. 2 is a side view of an ATV with the engine of the present inventionpositioned thereon, the details of the ATV being shown in dotted-lineformat;

FIG. 3 is a top view schematic illustration of the ATV illustrated inFIG. 2, showing the positioning of the engine of the present inventionwith respect to the centerline of theATV;

FIG. 4 is a cross-sectional side view illustration of the enigne of thepresent invention, highlighting at least a portion of the oil flow pathwithin the engine;

FIG. 5 is a cross-sectional view of the relative positioning of the oilfilter with respect to the oil pump and oil pan;

FIG. 6 is an enlarged, cross-sectional view of the oil path connectingthe crankcase to the cylinder block;

FIG. 7 is a cross-sectional, side-view illustration of the engine of thepresent invention, showing the relative positioning of the piston andcrankshaft to the parking assembly;

FIG. 8 is a front view of the camshaft timing gear, illustrating themounting holes for the screws that connect the camshaft timing gear tothe camshaft;

FIG. 9 is cross-sectional side view illustration of the engine of thepresent invention, showing in detail the water flow through the coolingsystem associated therewith;

FIG. 10 is a cross-sectional view of a portion of the engine of thepresent invention taken along the line 10—10 in FIG. 9;

FIG. 11 is a cross-sectional view of a portion of the engine of thepresent invention taken along the line 11—11 in FIG. 9;

FIG. 12 is a cross-sectional side view illustration of a hand-crankedspring starter designed for use on the engine of the present invention;

FIG. 13 is a cross-sectional end view illustration of the hand-crankedspring starter shown in FIG. 12, taken along the line 13—13;

FIG. 14 is a perspective illustration of the combined blow-by gas oilseparator and camshaft of the engine of the present invention;

FIG. 15 is an exploded perspective illustration of the blow-by gas oilseparator and camshaft shown in FIG. 14;

FIG. 16 is an enlarged, cross-sectional side view illustration of aportion of the engine of the present invention, showing the blow-by gasoil separator and a portion of the camshaft;

FIG. 17 is a perspective illustration of the centrifugal weight for thedecompressor of the engine of the present invention;

FIG. 18 is a rear plan view of the housing of the blow-by gas oilspearator for the engine of the present invention;

FIG. 19 is an exploded, perspective illustration of the continuouslyvariable transmission of the engine of the present invention;

FIG. 20 is a cross-sectional side view illustration of the drive pulleyof the CVT in a state where the engine is operating at low speed;

FIG. 21 is a cross-sectional side view illustration of the driven pulleyof the CVT in a state where the engine is operating at low speed;

FIG. 22 is a cross-sectional side view illustration of the drive pulleyof the CVT in a state where the engine is operating at high speed;

FIG. 23 is a cross-sectional side view illustration of the driven pulleyof the CVT in a state where the engine is operating at high speed;

FIG. 24 is an enlarged cross-sectional view of a portion of the drivepulley of the CVT in a state where the engine is operating at low speed;

FIG. 25 is a cross-sectional side view illustration of the slide sleevefrom the drive pulley of the CVT of the present invention;

FIG. 26 is a top view of the slide sleeve from the drive pulley of theCVT of the present invention;

FIG. 27 is a perspective, side-view of the slide sleeve of the drivepulley of the CVT of the present invention;

FIG. 28 is a perspective illustration of the guide member element of thedriven pulley of the CVT of the present invention;

FIG. 29 is a perspective illustration of the connector of the drivenpulley of the CVT of the present invention;

FIG. 30 is a perspective illustration of the inner half of the drivenpulley of the CVT of the present invention;

FIG. 31 is a rear view illustration of the inner half of the drivenpulley of the CVT of the present invention;

FIG. 32 is an enlarged, top view illustration of an alternate embodimentone of the centrifugal weights pivotally attached to the outer half ofthe driven half of the CVT of the present invention;

FIG. 33 is a cross-sectional side view illustration of an alternativedriven pulley for the CVT of the present invention, showing theconstruction for a pneumatically-operated driven pulley;

FIG. 34 is a cross-sectional view of the gear mechanism of thetransmission of the present invention;

FIG. 35 is a cross-sectional view of a portion of the transmission andgearing mechanism of the engine of the present invention;

FIG. 36 is an enlarged cross-sectional side view illustration of one ofthe toothed wheels of the transmission and gearing mechanism of theengine of the present invention;

FIG. 37 is an enlarged portion of the gearing mechanism of the engine ofthe present invention;

FIG. 38 is an enlarged portion of the gearing mechanism of the presentinvention, shown in a non-parked mode; and

FIG. 39 is an enlarged portion of the gearing mechanism of the presentinvention, shown in a parked mode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

To facilitate an understanding of the present invention, the followingdescription is divided into a number of subparts.

Although the description that follows is directed to a single cylinder,internal combustion engine with an associated CVT, it should be notedthat the invention is not limited to such. Instead, the features of thepresent invention may be applied to any type of internal combustionengine, as would be appreciated by those skilled in the art. Forexample, the features of the present invention may be applied to amultiple-cylinder, in-line, v-type, or opposed cylinder engine withoutdeviating from the scope of the present invention.

Furthermore, while the present invention preferably includes a CVT foruse with a single cylinder engine, those skilled in the art wouldreadily appreciate that the CVT of the present invention could be easilyused with any other type, style, or size of internal combustion engine.Moreover, while a CVT is preferred for use with the engine of thepresent invention, it would be readily appreciated by those skilled inthe art that a standard gear shift could be substituted for the CVTwithout deviating from the scope of the present invention.

In addition, while the engine and CVT of the present invention have beenspecifically designed for use in an ATV, which is the preferred use forthe present invention, the present invention is not limited just to useon ATVs. To the contrary, the present invention may be used in anyvehicle type, including cars, scooters, motorcycles, and other suitablevehicles.

1. The Engine, Generally

The engine of the present invetion is generally designated 10 throughoutthe drawings. The engine 10 includes a crankshaft 12 mountedtransversely to the centerline 14 thereof. This construction is commonfor engines used in vehicles such as motorcycles, for example.

As mentioned above, the engine 10 is designed to be mounted preferablyon the frame 17 of an ATV 16. One possible design for the ATV 16 isshown in dotted lines in FIG. 2. As illustrated, the engine 10 ispositioned between the front wheels 18 and the rear wheels 20 of the ATV16. A top schematic view of the position of the engine 10 in the ATV 16is provided in FIG. 3. While the specific positioning of the engine 10on the frame 17 of the ATV 16 is one feature of the present invention,the specific positioning will be described in greater detail below,following the discussion of the individual components that make up theengine 10 and the CVT 26 of the present invention.

In the preferred embodiment of the present invention, the engine 10 iscarburetted. However, the present invention is not meant to be limitedsolely to carburetted engines. To the contrary, it is contemplated thatthe engine 10 could be provided with any other type of fuel deliverysystem without departing from the scope of the present invention. Inparticular, it is contemplated that the engine 10 of the presentinvention could be provided with a suitable fuel injection system.

In the preferred embodiment of the ATV 16 of the present invention,which is illustrated in FIG. 3, the intake side 22 of the engine 10faces the rear of the ATV 16 and the exhaust side 24 of the engine 10faces the front. While this orientation of the engine 10 in the ATV 16is preferred, it is contemplated that the orientation of the engine 10could be reversed without deviating from the scope of the presentinvention.

As illustrated in FIGS. 1-3, the engine 10 is provided with a CVT 26,the moving components of which are enclosed within a cover 28. The CVT26 is described in greater detail below. With the engine 10 in thepreferred orientation, as illustrated in FIG. 3, the CVT 26 ispositioned on the left hand side of the ATV 16.

The CVT 26 operatively communicates with an output shaft 30 through abevel gear 32 to provide power to the front wheels 18 and the rearwheels 20 of the ATV 16. Motive power for the four-wheel drive istransmitted to the output shaft 30 via the bevel gear 32. While anall-wheel drive is preferred for the ATV 16 of the present invention,the ATV 16 could be a front-wheel or rear-wheel drive variety withoutdeviating from the scope of the present invention.

Preferably, the cylinder 34 is positioned at the rear of the ATV 16. Insuch a position, the cylinder 34 creates free space for the driver'slegs between in front of the engine 10. The positioning of the cylinder34 to the rear of the ATV 16 also provides for storage space at thefront of the engine 10. While this orientation is preferred, it iscontemplated that the orientation of the engine 10 could be reversed180° so that the cylinder 34 faces the front of the engine and the CVT26 faces to the right-hand side of the AVT 16. Changing the orientationof the engine 10 has the further advantage of shifting the center ofgravity of both the engine 10 and the ATV 16 in a forward direction,which has advantages in ATVs that are more sporty than the one depictedin FIG. 2.

The cylinder 34 and cylinder liner 36 preferably are made ofconventional materials, such as AlSi alloys for the cylinder 34 and greycast iron for the cylinder liner 36. To assemble the combined cylinder34 and cylinder liner 36, the cylinder liner 36 preferably is held in amold and the cylinder 34 is cast around it.

In a more advanced approach, the cylinder liner 36 is deposited in thecylinder 34 by a plasma coating process or some other thermal sprayingprocess. If manufactured according to such a process, a separatecylinder liner 36 is not required. Instead, the cylinder 34, which ispreferably made from an aluminum alloy (e.g., AlSi), has awear-resistamt coating applied thereto. The coating is sprayed onto thesurface of the bore of the cylinder 34. The coating may be made of anysuitable material such as one based on iron or steel containing someother metallic components (e.g., Cr, Mo, C) and containing specificoxides (e.g., iron oxides).

2. The Generator, the Camshaft Chain Drive, and the Output Shaft

The engine 10 includes a generator 40. The generator 40 preferably is apermanently excited 3-phase generator in which a magnet wheel 42 rotatesaround stationary coils 44, as shown in FIG. 1. Such a construction forthe generator 40 offers a number of advantages over generators known inthe prior art where the coil rotates around a stationary magnet. First,the potential for generator failure is reduced because only the magnetwheel 42 rotates, not the coil 44. In addition, maintenance and repairtime for the generator 40 may be significantly reduced. Also, the weightof the rotating masses (i.e., the magnet wheel 42) can be reduced, whichreduces the overall vibration generated by the engine 10.

In the preferred embodiment of the present invention, the magnet wheel42 is constructed as an extrusion-molded part and is mounted on a hub46. The hub 46, in turn, is mounted onto a tapered portion of thecrankshaft 12 and secured there by a nut 48. The magnet wheel 42preferably is connected to the hub 46 by rivets 50. While the magnetwheel 42 is preferably connected to the crankshaft 12 in this manner, itis contemplated that the magnet wheel 42 could be connected to thecrankshaft in any number of alternate ways without deviating from thescope of the present invention.

A chain wheel 52 is positioned adjacent to, and at the inner side of,the generator 40. The chain wheel 52 is fixed to the crankshaft 12through any suitable means known to those skilled in the art. The chainwheel 52 drives the timing chain 54 that extends between the chain wheel52 and the timing gear 56 on the camshaft 58. It is contemplated thatthe chain wheel 52 may be attached to the crankshaft 12 via a nut (notshown). Alternatively, the chain wheel 52 may be affixed to thecrankshaft 12 via a key arrangement (also not shown) or via a force fit.While a nut is the preferred manner of connection between the chainwheel 52 and the crankshaft 12, any alternative connection may beemployed without deviating from the scope of the present invention.

The main bearing 60 of the output shaft 30 is positioned below the chainwheel 52, bewteen the position of the magnet wheel 42 and the crankcasehousing wall 62. The output shaft 30 is arranged in the partition planebetween the crankshaft housing wall 62 and the cover 64 of the pullstarter 66. With this construction, the engine 10 may be provided with acompact construction in the lateral direction.

The output shaft 30 is positioned relatively close to the centerline (orcentral axis) 14 of the engine 10 (see distance c in FIG. 3). Thisallows the engine 10 to be positioned in the frame 17 of the ATV 16 ineither a cylinder backward orientation (e.g., for utility AVTs such asthe one illustrated in FIG. 2) or a cylinder forward orientation (e.g.,for sport ATVs). As indicated above, the engine 10 preferably is mountedin acylinder backward position. However, also as indicated above, thepositioning of the engine 10 may be reversed 180° in the ATV 16 merelyby flipping the differentials to which the output shaft 30 connects. Theoutput shaft 30 preferably is adapted to project from both sides of theengine 10 so that both 4-wheel and 2-wheel drive modes may beaccommodated, as indicated above.

The engine 10 may be positioned as shown for regular utility ATV's(thereby providing more room for a step-through chassis) or may bereversed with the cylinder and intake in front for sport ATV's (whichgenerally do not include a step-through arrangement). In the reversedposition, with the intake manifold positioned in the air stream of thevehicle where the air is cooler than at the exhaust side of the engine10, high end power for a sport model, at the expense of low end torque,may be improved.

3. The Crankshaft and the Connecting Rod

The crankshaft 12 preferably is formed as a single piece construction.As would be known to those skilled in the art, a single piececonstruction for the crankshaft 12 offers a number of advantages interms of cost and strength. While an integral construction for thecrankshaft 12 is preferred, it is contemplated that the crankshaft 12may be assembled from a number of separate components, as also would beknown to those skilled in the art.

The crankshaft 12 is driven by the piston 38 via a connecting rod 68.Preferably, the connecting rod 68 is a crack-type member. This meansthat the lower end 70 of the connecting rod 68 is manufactured as anintegral part of the connecting rod 68. After casting, the lower end 70is cracked open. This is done by applying a force to the opening throughthe lower end 70 (that surrounds the crankshaft 12, when installed inthe engine 10). In this manner, the connection between the halves of thelower end 70 of the connecting rod 68 is improved considerably. Ofcourse, as would be appreciated by those skilled in the art, theconnecting rod 68 could be manufactured according to any other suitablemethod or process.

In the preferred embodiment of the present invention, the mountingbetween the crankshaft 12 and the connecting rod 68 is worthy of someadditional description. In particular, it is preferred that a slidebearing 72 be positioned between the connecting rod 68 and thecrankshaft 12. The provision of a slide bearing 72 in this locationdistinguishes the engine 10 of the present invention from engines in theprior art. In particular, similar enignes in the prior art incorporateantifriction (ball) bearings between the connecting rod and crankshaft.

When designing an engine, especially one that is expected to operate atextremely low temperatures (e.g., −30° C. and below), the type ofbearing inserted between the connecting rod and the crankshaft becomes asignificant concern. The problem is associated with the viscosity of thelubricating oil at such low temperatures. In particular, oil at lowtemperatures may become so viscous that it cannot flow properly in andaround the bearings between the connecting rod and the crankshaft. Ifthis occurs, the engine cannot operate because it cannot crank or turnover.

To avoid this problem, engines in the prior art incorporate antifrictionbearings between the connecting rod and the crankshaft. As a rule,engine designers avoided slide bearings, because it was believed thatthe viscosity of lubrication in slide bearings at low temperatures wouldbe too high to permit the engine to crank. Specifically, because of thetemperature dependence of the lubricants, the reduced bearing clearancein slide bearings was thought to result in hydrodynamic frictionalforces so high at low temperatures that too much torque would berequired to start the engine. To provide such a torque, it was thoughtthat the engine would require a stronger battery than desired or wouldrequire additional starting aid measures.

As it turns out, at least with respect to the engine 10 of the presentinvention, the slide bearing 72 does not hinder start up at lowtemperatures. In fact, it was discovered through testing that frictionbetween the piston 38 and the cylinder 34 (or cylinder liner 36) is theprimary impediment to starting the enigne 10 at low temperatures.Therefore, the increased friction in the slide bearing 72 (as comparedto an antifriction bearing) does not appear to lead to any substantialdeterioration of the cold starting properties of the engine 10.

While it is preferred to incorporate a slide bearing 72 between theconnecting rod 68 and the crankshaft 12, it is contemplated that theengine 10 of the present invention could incorporate any other type ofbearing at the same location. Specifically, as would be understood bythose skilled in the art, a conventional antifriction (ball or roller)bearing may be substituted for the slide bearing 72 without deviatingfrom the scope of the present invention.

As FIG. 1 illustrates, the crankshaft housing (or crankcase) 74 of theengine 10 is vertically partitioned, thus resulting in a very stiffstructure. The vertical partitioning of the crankcase 74 has anadditional advantage in that it is possible to arrange the bearings 76,78 more freely, since it is not necessary to arrange all the bearings76, 78 in the plane of partition (as would be required by engines in theprior art). For this reason, among others, it becomes possible to designthe engine 10 to be short and compact.

In addition to providing a slide bearing between the connecting rod 68and the crankshaft 12, the engine 10 of the present invention alsoprovides a bushing 80 between the upper end 82 of the connecting rod 68and the piston 38. As with the slide bearing 72 at the lower end 70 ofthe connecting rod 68, the provision of the bushing 80 at the upper end82 of the connecting rod 68 is also a departure from the teachings ofthe prior art. To avoid starting problems, engines in the prior art alsoincluded an antifriction (needle) bearing between the top of theconnecting rod and the piston. The bushing 80 in the engine 10 of thepresent invention preferably is made of nonferrous heavy metal. As wouldbe appreciated by those skilled in the art, however, the bushing 80 maybe made from any suitable material without deviating from the scope ofthe present invention.

4. The Balance Shaft

As illustrated in FIG. 1, a toothed wheel 82 operatively connects thecrankshaft 12 to a balance shaft 84. The balance shaft 84 extendsbetween antifriction bearings 86, 88 and provides mass balancing of thefirst order. As illustrated in FIG. 1, the toothed wheel 82 meshes witha toothed wheel 90 on the balance shaft 84. One difference between thegearing between the toothed wheels 82, 90 and the gearing between thecrankshaft and balance shafts in engines of the prior art is that, inthe engine 10, the gearing is spiral. A spiral gearing is better than anon-spiral gearings because it is quieter than a non-spiral (or regulargearing).

The engine 10 also differs from the construction taught by the prior artin that the toothed wheels 82, 90 intermesh within the interior space 92of the crankcase 74. In this position, the toothed wheels 82, 90 arepositioned between the two bearings 86, 88 at either end of the balanceshaft 84 and also between the slide bearings 76, 78 at either end of thecrankshaft 12. Advantageously, placing the toothed wheels 82, 90 in thisposition avoids a space conflict with the output shaft 30. At the sametime, excellent lubrication of the toothed wheel gears 82, 90 isensured. Moreover, with such a construction, use of the space 92 isimproved over engines in the prior art, making it possible to constructa compact engine 10.

As discussed above, unlike the crankshaft 12, the balance shaft 84preferably is mounted in antifriction bearings 86, 88. However, as wouldbe appreciated by those skilled in the art the antifriction bearings 86,88 may be replaced with other bearings without deviating from the scopeof the present invention. For example, the antifriction bearings couldbe replaced with slide bearings.

5. The Oil Circuit

An oil pump 94 is operatively connected to the end of the balance shaft84 exteriorly to the crankcase housing wall 62, as illustrated in FIG.4. So constructed, the balance shaft 84 drives the oil pump 94.Specifically, the end of the balance shaft 84 is provided with a toothedgear 100 that is connected, through at least one additional gear (notshown), to a drive gear (not shown) associated with the oil pump 94. Ofcourse, as would be appreciated by those skilled in the art, the oilpump 94 could be connected to the balance shaft 84 by a single gear, aplurality of gears, or any other suitble connecting arrangement.

As shown in FIG. 4, the oil pump 94 preferably is positioned as far tothe bottom 96 of the crankcase 74 as possible. Such a positioningreduces the suction height from the bottom 96 of the crankcase 74 to theoil pump 94, thereby reduding the danger of an irregular flow pattern ofoil to the oil pump 94. Positioning the oil pump 94 near the bottom 96of the crankcase has the further advantage of minimizing (or preventing)air from being sucked into the oil passage with the oil from the oil pan102, thereby helping to minimize or prevent foaming and cavitationwithin the oil pump 94. This feature is particularly important for anengine designed for use on an ATV (such as the engine 10 of the presentinvention), because the engine 10 may operate at very low temperatures(−30° C. or lower). At these low temperatures, oil viscosity increasessignificantly, which means that the oil's resistance to flow alsoincreases porportionally.

It is preferred that the oil pump 94 be a conventional, rotary pistonpump (trochoidal pump). In addition, it is preferred that the oil pump94 supply the engine 10 with the required amount of oil by means of awet-sump pressure lubrication. Alternatively, the oil pump 94 could be agear pump without deviating from the scope of the present invention.

As illustrated in FIG. 4, the oil circuit, which is shaded to facilitatean understanding of the oil flow path, includes a pressure relief valve98, which acts as a safety device that opens upon sensing an oilover-pressure.

When the engine 10 is operating, oil is sucked by the oil pump 94 fromthe wet sump (oil pan) 102 via a coarse filter sieve 104. The oil pump94 is positioned in the middle of the engine housing so that the oilpump inlet dips into the wet sump 102. So positioned, the engine 10 isexpected to be able to self-lubricate regardless of the angularorientation (preferably, up to 45°) of the ATV 16 carrying it.

The oil leaves the oil pump 94 and flows directly to the oil filter 106where fine particulate materials, such as carbon, are removed therefrom.As illustrated in FIG. 1 and, in greater detail, in FIG. 5, the oilfilter 106 is positioned above the oil pump 94, roughly at the sameelevation from the bottom 96 of the engine 10 as the crankshaft 12, andincludes an oil filter cover 108 affixed to the engine 10 by a single,central screw 110. When the central screw 110 is removed from the filtercover 108, the oil drains through the central threaded hole, which isopened when the central screw 110 is removed. A seal 114 surrounds theoutward end 116 of the central screw 110.

The oil filter 106 is surrounded by a cooling water jacket 118. Coolingwater is circulated through the jacket 118 to remove heat from the oilpassing through the oil filter 106. The water pump casing 120 and theengine cover (generator cover) 122 also form part of the housing for theoil filter 106.

The position of the oil filter 106 is worthy of particular attention.Since ATV's 16 are often operated under extreme conditions, significantdemands typically are placed on the engines 10. Increased demand on theengine 10 results in an increased entrapment by the oil of carbonparticles, which directly result from the combustion of fuel. Becausethe oil in the engine 10 of the present invention is expected to entrapparticulate material more quickly than an engine designed for use on avehicle other than an ATV 16, the replaceable portion 124 (i.e, thedisposeable or recycleable portion) of the oil filter 106 will need tobe replaced more frequently.

The design of the oil filter 106 of the present invention greatlyfacilitates removal and replacement of the replaceable portion 124. Onan ATV 16, because the engine oil and replaceable portion 124 of the oilfilter 106 are more frequently changed, the ease of changing the engineoil and filter 124 are of increased importance. For this reason, readyaccess to the oil filter 124 in the engine 10 is a particularlyattractive feature of the engine's 10 design.

From the oil filter 106, the oil flows towards a distribution point 126,as illustrated in FIG. 4. From the distribution point 126, the oil flowsin two directions: (1) toward the main bearings of the crankshaft 12,and (2) into a bore 128 leading to a flange 130 at the base of thecylinder block 132. The oil path toward the main bearings of thecrankshaft is designated 134. The oil direction toward the cylinderblock 132 is designated 136. In the direction 136, the oil passes an oilpressure transducer 138.

As illustrated in FIG. 6, the oil enters the cylinder block 132 via agroove 140. The upper end of the crankshaft housing 74 defines anannular gap 142 between a locking screw 144 that attaches the cylinderhead 146 and cylinder block 132 to the crankcase 74. In the annular gap142, the oil rises upwardly and, at the upper end of the cylinder head146, is directed via a bore (not shown) below the screw head towards thehollow rocker arm shaft 148. The rocker arm shaft 148 is affixed in thecylinder head 146 via two screws. Preferably, the rocker arm shaft 148is made as a single piece construction. It is contemplated, however thatthe rocker arm shaft 148 may be made from a number of separatecomponents.

The oil enters the interior of the rocker arm shaft 148 and emergesthrough small bore holes 150 in the rocker arm shaft 148. Accordingly,it provides adequate lubrication of the rocker arm bearings 152. Fromthere, the oil flows to the camshaft bearings 154, 156, which arepositioned therebelow, as shown in FIG. 1.

As shown in FIG. 1, below the camshaft 58, the oil accumulates in asmall basin 158 in which the lobes 160 of the camshaft 58 areperiodically immersed for lubricating purposes. The degree to which thebasin 158 is filled, however, is not so high so as to negatively effectlubrication (e.g., by foaming). The oil flows from the basin 158 througha channel 162 in the cylinder head 146 toward the upper gear 56 to whichthe camshaft 58 is attached. From the channel 162, the oil drains backto the wet sump 102. During its flow to the wet sump 102, the oillubricates the timing control chain 54.

The camshaft timing gear 56 is provided with a blow-by gas separator164, the details of which will be provided below. The camshaft timinggear 56 preferably is connected to the camshaft 58 by means of threescrews 168 (only one of which is visible in dotted lines in FIG. 1).

To guarantee mounting of the camshaft timing gear 56 in the correctposition, the screws 168 pass through holes 170 that are arrangedasymmetrically about the central hole 172. FIG. 8 illustrates thisfeature. As with any gear, camshaft timing gear 56 is provided with anumber of teeth 174 that mesh with the timing chain 54.

While not illustrated in detail in the drawings appended hereto, exceptin gross detail in FIG. 7, the connection between the rocker arms 176and the intake and exhaust valve stems 178 differs from the prior art.Specifically, the rocker arms 176 are provided with hydraulic valveclearance balancing elements 180 on the sides facing the valve shafts,each comprising a ball socket abutting on the upper end of therespective valve stem 178. The rear side of the plunger-like balancingelements 180, which are mounted in bores of the rocker arms 176, areprovided with pressurized oil via a bore 182. This bore 182 opens fromthe bearing site on the respective rocker arm shaft 148. In this manner,the hydraulic valve clearance balancing elements 180 receive pressurizedoil from the interior of the rocker arm shaft 148 via the radial bores184 thereof.

6. The Camshaft, the Rocker Arm Axle, the Valves, and the Cylinder HeadCover

In the present design of the engine 10, the rocker arms 176 are believedto be adequate for operation of the design. However, it is preferredthat the rocker arms 176 be light in weight. While “heavy” rocker armsdo not impede operation of the engine 10, attempts have been made toreduce the weight of the rocker arms 176. At present, it is preferredthat the rocker arms 176 be made of aluminum, as is common in theautomobile industry. Rocker arms 176 made from aluminum, however, giverise to problems of stiffness or strength, respectively. Therefore, itis conceivable that the rocker arms could be made of steel.Alternatively, the rocker arms 176 may be made from an alloy containingaluminum or iron. As would be appreciated by those skilled in the art,to practice the present invention, the exact composition of the rockerarms 176 does not require only the materials recited herein.

The connection between the cylinder head 146 and the cylinder head cover188 is acoustically decoupled. According to FIG. 1, various elastomerelements or gaskets 186, respectively, are attached between the cylinderhead 146 and the cylinder head cover 188. In this manner, direct soundpropagation from the cylinder head 146 to the cylinder head cover 188 isblocked. To further prevent the propagation of sound from the cylinderhead 146 to the cylinder head cover 188, the fixing screws are alsoacoustically decoupled.

7. The Water Cooling System (Air Cooling, Optional)

Like the oil pump 94 for the engine 10 of the present invention, a waterpump 190 is driven by the balance shaft 84. The position of the waterpump 190 in the engine 10 is best illustrated in FIG. 9. Preferably, thewater pump 190 connects to the balance shaft 84 via a toothed wheel. Thetoothed wheels that drive both the water pump 190 and the oil pump 94preferably are made of non-metallic materials, such as plastic. Ofcourse, as would be appreciated by those skilled in the art, however,the toothed driving wheels may be construced from metal or any othersuitable material. Like the oil filter 106, the water pump impeller 192is disposed in the water pump casing 120.

In the direction indicated by the arrow 194, water enters the water pump190 from a cooling heat exchanger (not shown) that is connected to theengine 10. Immediately after its emergence from the water pump 190, thewater flows towards the oil filter 106 in the direction of arrow 196.The cooling water then enters the oil filter cooling jacket 118 disposedaround the oil filter 106.

The positioning of the water pump 190 adjacent to both the oil filter106 and the oil pump 94 is a significant improvement over engine designsin the prior art. In particular, the close proximity of these threeelements to one another permits for the construction of a compact engine10. In addition, the prior art fails to show or suggest that water fromthe water pump 190 may be directed through a water passage 118 aroundthe oil filter 106 to affect cooling of the oil within the engine 10.

From the water jacket 118 around the oil filter 106, the water changesits flow direction and travels upwardly toward the cylinder head 146, asindicated by the arrow 198. The cooling water passes through thecylinder block 132, in the direction shown by the arrow 200. After thecylinder block 132, the water continues to flow upwardly until it flowsthrough the passages in the cylinder head 146 to cool the intakepassages 202 and exhaust passages 204.

As illustrated in FIG. 10, the crankcase 74 preferably contains fourseparate passageways 206, 208, 210, 212. The water rises through thepassageways 206, 208, 210, 212 until it fills the cooling water jacket214 that surrounds the cylinder 134 in the cylinder block 132, asillustrated in FIG. 11.

As shown in FIG. 11, the cylinder block 132 has an open-deckconstruction. This means that water flows spirally around the cylinder134 in the jacket 214, which nearly encircles the entire circumferenceof the cylinder 134. The only portion of the cylinder 134 not surroundedby the water jacket 214 is the portion containing the timing chainpassage 216. It should be noted, however, that the water jacket 214 maytake any suitable shape around the cylinder 134 to affect proper coolingof the cylinder 134 and cylinder liner 136.

A cylinder head gasket 218 is positioned between the cylinder block 132and the cylinder head 146 to provide a sufficient seal between the twosections of the engine 10. The gasket 218 is provided with a number ofholes therethrough to permit the water to flow from the cylinder block132 to the cylinder head 146.

While not shown, the holes in the gasket 218 have a predeterminedcross-sectional area and act as throttles. The holes adjust the quantityand flow pattern of the water passing therethrough. In particular, theholes in the gasket 218 are positioned and designed to provide a greateramount of water flow on the side of the engine 10 with the exhaustpassages 204 than the intake side 22 of the engine 10. In this manner,the exhaust side 24 of the engine 10 receives a greater amount ofcooling than the intake side 22. Since water flow is greater on theexhaust side 24 of the engine 10, the water flows from the exhaust side24 to the intake side 22 of the engine 10. Accordingly, the water firstcools the exhaust valve stems 220 before cooling the intake valve stems222. After the water cools the intake valve stems 222, the water exitsfrom the engine 10 through an outlet 224, which is illustrated in FIG.4. From the outlet 224, the water returns to the heat exchanger (e.g., aradiator) where it is cooled before returning to the water pump 190.Before leaving the cylinder head 146, the water passes a thermostat 224and a sensor 226, which monitors the water temperature. The thermostat224 opens when the water temperature 226 exceeds a given threshold.

Optionally, while not the preferred embodiment for the presentinvention, the water cooling system may be omitted altogether. With sucha design, the engine 10 may be cooled by air. Since, with the low speedsof ATVs, air cooling is not usually sufficient to maintain the engine atan appropriate temperature, an air stream may be directed from the CVT26 to the cylinder 134 and cylinder head 146.

8. The Starting Mechanism

It is preferred that the engine 10 of the present invention be startedusing a starter motor 230, the location of which is illustrated in FIG.4. Preferably, the starter motor 230 is connected to the engine 10 via adrive gear (not shown), which drives an intermediate gear/Bendix driveassembly (not shown). The intermediate gear, in turn, drives a startergear 232, which is illustrated in FIG. 19.

The starter gear 232 is incorporated as a part of the inward half of thedrive pulley 234 of the CVT 26, which is described in greater detailbelow in connection with the CVT 26. The starter gear 232 preferably isconnected to the drive pulley inner half 234 by screws 236, asillustrated in FIG. 20. The starter gear 232 forms the inner most sideof the drive pulley inner half 234 such that the inner side of the drivepulley inner half 234 is partially closed. Since the drive pulley innerhalf 234 acts as a fan to cool the components of the CVT 26, using thestarter gear 232 to partially close the inner side of the drive pulleyinner half 234 increases air circulation within the CVT. As a result,all of the components beneath the CVT cover 28 receive a more pronouncedair-cooling.

In addition, the weight of the starter gear 232 is preferably arrangedso that the starter gear 232 is a ring gear. This helps to increase theinertia of the crankshaft 12. Because of this, the starter gear 232serves as a flywheel for the crankshaft 12. The starter gear 232 alsomay be provided with balancing holes during the manufacture of the CVT26. In particular, to assure proper balancing between the drive pulley322 and the crankshaft 12, weight may be removed from the starter gear232 in specific locations. The weight balance, therefore, may differfrom engine 10 to engine 10 depending on the conditions surrounding themanufacture of the engine.

Since the engine 10 of the present invention is designed for use on anATV 16, it is likely that the ATV 16 will be driven to locations remotefrom assistance. Accordingly, one design consideration is the provisionof alternative means for starting the engine 10, should the startermotor 230 fail.

As a redundant feature added to the starting system of the engine 10, acable pull starter 66 also may be provided, as illustrated in FIG. 1.Preferably, the cable pull starter 66 is mounted outwardly of thegenerator 40. The central shaft 238 of the pull starter 66 operativelyconnects to the crankshaft 12 to impart rotational motion from the pullstarter 66 to the crankshaft 12.

In addition, as illustrated in FIGS. 12 and 13, the engine 10 of thepresent invention may be provided with a manually-operated springstarter 240. In the preferred embodiment of the present invention thatincludes the spring starter 240, the spring starter 240 is affixed tothe generator 40 of the engine 10. The spring starter 240 includes ahousing 242 with a central shaft 244. A spring 246 is wrapped around thecentral shaft 244 and, for the most part, remains in a relaxed (orunwound) condition, as shown in FIGS. 12 and 13. The spring starter 240is provided with a hand crank 248 with a connecting pin 250, whichengages a receiving hole 252 in the central shaft 244.

To start the engine 10, the connecting pin 250 of the hand crank 248 isinserted into the receiving hole 252. Then, the hand crank 248 isrotated in the direction of arrow 254 to wind the spring 246. When thespring 246 is sufficiently wound, the energy stored in the spring 46 maybe released to assist the operator in starting the engine 10. While thespring starter 240 may be used by itself, it is preferred that thespring starter 240 be used in combination with either the starter motor230 or the pull starter 66. If used with the starter motor 230, thespring starter will have the configuration illustrated in FIG. 12.Namely, the spring starter 240 will be mounted on the generator 40. Ifthe engine 10 is provided with a pull starter 66, as illustrated in FIG.1, the spring starter 240 may be positined between the generator 40 andthe pull starter 66. Alternatively, the spring starter 240 may bepositoned outwardly from the pull starter 66.

The actual positioning of the spring starter 240 is not relevant to thepresent invention. The spring starter 240 may be provided to assist instarting the engine 10 under at least two separate conditions. The firstis where the starter motor 230 does not provide sufficient torque toturn the engine 10 over. It is believed that this may occur when theoperator attempts to start the engine 10 at low temperatures. The secondis where the engine 10 is provided with a pull starter 66 and theoperator is not strong enough to start the engine 10 with the pullstarter 66. In either case, the spring starter 240 will store asufficient amount of energy to assist in starting the engine 10.

As discussed above, the spring starter 240 preferably is designed toassist in starting the engine 10. As such, only a substantially slightlygreater energy must be applied to set the engine into motion than wouldbe applied without the spring starter 240. Accordingly, the spring 246is dimensioned and biased such that the piston 38 and the spring 246counterbalance each other slightly before the upper dead center positionof the piston 238.

In still another alternative embodiment, it is contemplated that thespring starter 240 could be designed to start the engine 10. In such acase, the spring starter would act as the starter for the engine 10 andnot as an assistance to the starting of the engine 10.

A further development (in ATVs) for facilitating starting of the engine(especially cold start) is the “decompressor” 256 illustrated in FIGS.14-18. As shown in cross-section in FIG. 16, the decompressor 256 ismounted on the camshaft timing chain gear 56.

The decompressor comprises two main components, a centrifugal weight 258and a pin 260, the so-called “deco”-axle. During a standstill and at alow number of revolutions (below idle speed) of the engine 10, the pin260 is in a position where its tip 262 is inserted in the direction ofthe camshaft 58, away from the camshaft timing chain gear 56. When inthis position, the tip 262 projects radially over the base circle of thefirst cam. During rotation of the camshaft 58, the tip 262 forces theassociated rocker arm 176 to move over the “deco”-axle 260 so that therocker arm 176 is pivoted an additional upward distance on the rockerarm axle 148. Because of the additional movement of the rocker arm 176,the associated valve remains opened for a slightly longer period. Sincethe valve is opened during compression for a slightly longer period,compression within the cylinder 134 is reduced and the engine 10 can bestarted with substantially greater ease.

The deco-axle 260, however, does not remain in the decompressionposition during all engine speeds. To the contrary, once the enginespeed (in revolutions per minute or rpm's) exceeds a predeterminedamount, the centrifugal weight 258 swings radially outward about itspivot axis 264. The motion of the centrifugal weight 258 is bestillustrated in FIG. 18.

As shown in FIG. 18, at low engine speeds, the centrifugal weight 258remains in its initial position 268, which is illustrated in dottedlines. As the speed of the engine 10 increases, however, the centrifugalweight 258 shifts outwardly about its axis 264 to its final position270, which is shown in solid lines.

The centrifugal weight 258 is pivotally mounted to the camshaft timingchain gear 56. Specifically, the centrifugal weight 258 is manufacturedwith a circular opening 272 that mates with a flange 274 that pivotallyslips over the outside surface of one of the screws 168 that connect thecamshaft timing chain gear 56 to the camshaft 58, as illustrated inFIGS. 14 and 15. The centrifugal weight 258 is biased in the initialposition 268 by a spring 276. The spring 276 provides a sufficientamount of biasing force to maintian the centrifugal weight 258 in theinitial position 268 until the speed of the engine 10 exceeds apredetermined threshhold amount.

The centrifugal weight is provided with an elongated tooth 278 on aninner surface 280 thereof. As shown in FIG. 17, the elongated tooth 278extends substantially from a first side 282 to a second side 284 of thecentrifugal weight 258. The elongated tooth engages a groove 286 on thedeco-axle 260. As the centrifugal weight 258 moves from the initialposition 268 to the final position 270, the elongated tooth 278 appliesa force on the deco-axle 260 that forcibly pulls the tip 262 of the decoaxle 260 toward the camshaft timing chain gear 56. In this manner, thetip 262 of the deco-axle 260 is withdrawn from the base circle of thefirst cam. Accordingly, the deco-axle 260 no longer performs adecompression function and the engine 10 operates according to a“regular” or unmodified compression schedule, which means that theassociated valve remains closed in the angular range in question duringcompression, and the engine 10 compresses the fuel-air mixture as usual.The axial movement of the deco-axle 260 is effected by the special kindof connection between the deco-axle 260 and the centrifugal weight 258.Specifically, the elongated tooth 278 that engages the deco-axle isformed like an inclined plane. As such, the elongated tooth 278 forcesan axial stroke as soon as the centrifugal weight 258 moves radiallyoutwardly.

The spring 276 ensures that the centrifugal weight is drawn back to itsinitial position 268 when the engine speed falls below the predeterminedthreshhold. Under those conditions, the deco-axle 260 is pushed axiallyinward so that the decompressor 256 becomes active again. Duringstartup, the decompressor 256 preferably prevents a substantialcompression for a few revolutions. In particular, with the presentdesign, the decompressor 256 starts to function ≈38° before the upperdead center position of the piston 38.

9. The Blow-by Gas Oil Separator

FIGS. 14-18 also illustrate a blow-by gas oil separator 288 that isincorporated into the engine 10 of the present invention. The blow-bygas oil separator 288 removes oil from the blow-by gas before theblow-by gas exits the crankcase 74 through a blow-by gas outlet 290 andis directed to the induction system, e.g., to the airbox (not shown).

The blow-by gas separator 288 preferably includes a housing 292 that isprovided with several locking tabs 294 about its periphery. The lockingtabs 294 extend through locking holes 296 disposed through the camshafttiming chain gear 56, as illustrated in FIG. 16, to engage the rearsurface of the camshaft timing chain gear 56. The housing 292 preferablyis made from a light-weight material such as plastic. However, as wouldbe appreciated by those skilled in the art, the housing 292 may be madefrom any other suitable material including metal.

The housing 292 defines a plurality of uniformly-sized holes 298 alongpart of its outer edge that permit entry of the blow-by gas flowing fromwithin the crankcase 74 to the induction system. The housing alsocontains a further hole 300 that is larger than the uniformly-sizedholes 298. All of the holes 298, 300 act as entry points for the blow-bygas to enter the housing 292. Once inside the blow-by gas separator 288,the blow-by gas, which generally has a very low pressure, is subjectedto centrifugal forces because the housing 292 spins in the directionshown by arrow 302. Due to centrifugal forces, the oil in the blow-bygas, which is in the form of very fine droplets, separates from theblow-by gas and impacts against the inner wall 304 of the housing 292.The oil then tends to travel along the inner wall 304 in the directionindicated by arrow 306 such that the oil flows toward the holes 298. Theoil drains from the housing through the holes 298 and also through oildrain ports 308 provided through the side of the housing 292.

The interior of the housing 292 is provided with a labrynthineconstruction to delay the blow-by gas therein for a sufficiently longtime to centrifuge substantially all of the oil from the gas. Thelabrynthine construction is illustrated best in FIG. 18. In particular,the housing includes a radial separating wall 310 extending from theside wall 312 toward the central opening 314 in the housing 292. Acircumferential separating wall 316 extends partially along the interiorof the housing at a position radially inward of the holes 298. Two sideseparating walls 318 extend from the side wall 312 and extend toward theradial separating wall 310. Together, the walls 310, 316, 318 define thelabrynthine path for the blow-by gas, which is indicated by arrow 320.

The labrynthine path 320 through the housing 292 ensures that amajority, if not substantially all, of the oil is removed from theblow-by gas before the gas exits the crankcase 74 through the outlet290.

The housing 292 is designed to by symmetrical about the radialseparating wall 310. So designed, the housing 292 could be adapted to beused on an engine that rotates in a direction opposite to the rotationdirection 302. Also, beause of its symmetrical construction, the housing292 may be employed on a V-type engine where the camshafts rotate indirections opposite to one another during operation.

10. The CVT (Continuously Variable Transmission)

The CVT 26 of the present invention is illustrated in FIGS. 19-33. TheCVT 26 comprises a drive pulley 322 and a driven pulley 324. Both thedrive pulley 322 and the driven pulley 324 have inner and outer halves.The inner half of the drive pulley is designated 234. The outer half ofthe drive pulley is designated 326. The driven pulley inner half isdesignated 328 while the outer half is designated 330.

Since the drive pulley 322 is connected to the crankshaft 12 asillustrated in FIG. 1, torque is transmitted from the crankshaft 12 tothe drive pulley 322. A belt 332 connects the drive pulley 322 to thedriven pulley 324, permitting the torque to be transmitted to the drivenpulley 324.

FIGS. 20 and 21 illustrate the positions of the drive pulley 322, thedriven pulley 324, and the belt 332 when the engine 10 is operating at alow engine speed. FIGS. 22 and 23 illustrate the respective positions ofthe drive pulley 322, driven pulley 324 and belt 332 when the engine 10is operating at high engine speeds. Any intermediate positons betweenthese extremes would indicate that the engine 10 is operating at anintermediate speed.

The CVT 26 operates in the following manner.

The drive pulley inner half 234 is provided with a belt engagementsurface 334. The drive pulley outer half 326 is provided with a beltengagement surface 336. Similarly, the driven pulley inner half 328includes a belt engagement surface 338. Finally, the driven pulley outerhalf 330 includes a belt engagement surface 340. The belt 332 extendsbetween the drive pulley 322 and the driven pulley 324 and, duringoperation, predominantly engages the belt engagement surfaces 334, 336and 338, 340, respectively. The belt 332 transfers the torque of theengine 10 from the drive pulley 322 to the driven pulley 324.

The drive pulley inner half 234 includes the starter gear 232, which isconnected thereto via one or more screws 236. The drive pulley innerhalf 234 is connected to the crankshaft 12. The drive pulley outer half326 is biased by a drive pulley spring 342 away from the drive pulleyinner half 234 when the engine 10 operates at low speeds.

The drive pulley outer half 326 is provided with a number of centrifugalweights 344 that are mounted to pivot axes 346 disposed about theperiphery of the rear surface of the drive pulley outer plate member348. The outward surfaces 350 of the centrifugal weights rest againstrollers 352 on the drive pulley roller member 354.

The drive pulley spring 342 exerts sufficient force on the drive pulleyouter half 326 to force the outer half 326 away from the inner half 234.In particular, the drive pulley spring 342 exerts its force on the outerplate member 348. The centrifugal weights 344 on the outer plate member348, in turn, contact the roller member 354. Due to the force exerted bythe drive spring 342, the centrifugal weights 344 are in constantengagement with the rollers 352. The force of the drive spring 342biases the outer half 326 of the drive pulley 322 away from the innerhalf 234, as shown in cross-section in FIG. 20.

At low engine speeds, the inner half 234 and the outer half 326 of thedrive pulley 322 are positioned as illustrated in FIG. 20. However, athigh speeds, the halves 234, 326 take the positions shown in FIG. 22.The centrifugal weights 344 are instrumental in making this transitionalchange. In particular, as the rotation speed of the drive pulley 322increases, the centrifugal force on the centrifugal weights 344 becomessufficiently high that the centrifugal weights 344 begin to swingoutwardly in the direction of arrow 356. The greater the rotationalspeed, the greater the outward swing of the weights 344 until theweights 344 reach their maximum outward swing and the rollers 352 restagainst the stops 358 on the centrifugal weights 344. The maximum swingposition is illustrated in FIG. 22.

As the centrifugal weights 344 swing outwardly, their outer surfaces 350press against the rollers 352. This causes the drive pulley outer platemember 348 and the roller member 354 to separate from one another,collapsing the drive spring 342. As a result, the belt engagementsurface 334, 336 move toward one another. Since the belt 332 is angledto ride on the belt engagement surfaces 334, 336, and since it iseffectively incompressible (albeit elastic), the belt 332 travelsoutwardly from the inner position shown in FIG. 20 to the outer positionillustrated in FIG. 22.

Since the tension on the drive belt 322 must remain constant regardlessof the position of the belt 322 in the CVT 26, the driven pulley 324acts in a manner opposite to that of the drive pulley 322. Inparticular, the driven pulley 324 includes a driven spring 360 thatforces the inner half of the driven pulley 328 toward the outer half ofthe driven pulley 330 in the rest (or low speed) condition. Therefore,when the engine 10 operates at a low speed, the inner and outer halves328, 330 of the driven pulley 324 are at their closest point to oneanother, as illustrated in FIG. 21.

When the engine 10 is operating at high speed, however, the tension onthe belt 332, which must remain constant to avoid breakage of the belt332, causes the inner and outer halves of the driven pulley 324 toseparate. Accordingly, the belt 332 travels from its highest point asshown in FIG. 21 to its lowest point, as illustrated in FIG. 23.

The CVT 26 of the present invention differs from the prior art isseveral respects. First, the CVT 26 is designed so that it is possibleto equip the ATV 16 with a brake assembly that may be engaged while theengine 10 is operating. The brake assembly 362 is illustrated in FIGS.34-39, below and is discussed in greater detail in connection with thosedrawings below. Second, the CVT 26 is designed so that the ATV 16 may betowed or pushed so that the transmission can be used to start the engine10. In both cases, the direction of the transmitted torque is changedfrom a positive direction (where the engine 10 drives the vehicle) to anegative direction (where the wheels 18, 20 drive the engine 10 or theengine 10 brakes the vehicle). The latter condition (i.e., the negativedirection) will be referred to as a “reverse torque transmission” modeor a “RTT” mode in the description that follows.

Prior art CVTs with a RTT are known. These prior art CTVs, however, relyon conventional CVT design parameters. One example of such a CVT is madeby Polaris®, a snowmobile manufacturer located the United States.Polaris's snowmobile incorporates a CVT based on a poly-V-sectionbelt/drive pulley combined with a conventional freewheel and clutchunit. The poly-V-section belt and pulley engage one another when thebelt is in the low speed position on the drive pulley (analogous to theposition illustrated in FIG. 20). This design, however, has at least onesignificant drawback. The elastic belt becomes significantly worn whenit engages the pulley section and thus tends to fray, thereby greatlyreducing its useful life.

To overcome difficulties such as these, and to provide the ability tobrake the ATV 16 when the engine 10 is operating, and to provide a RTT,a mechanism to permit free wheel operation was developed for the CVT 26of the present invention. In particular, the CVT 26 of the presentinvention incorporates a slide sleeve 364 on the drive pulley 322. Theslide sleeve 364 cooperates with one or more spring loaded pins 366 toaffect its operation. An enlarged view of the slide sleeve 364construction is provided in FIG. 24.

The slide sleeve 364 has two modes of operation. The first is thenon-engaged mode where the slide sleeve 364 permits the inner and outerhalves 234, 326 of the drive pulley 322 to rotate without imparting anytorque to the belt 332. This operational position is illustrated in FIG.21. The second operational mode permits the CVT 26 to act as a RTT toimpart torque from the wheels 18, 20 of the ATV 16 to the engine 10.

To permit free rotation of the slide sleeve 364, the sleeve 364 isjournaled by two anitfriction bearings 368, 370 on shaft 374. Inoperation, when the engine 10 is operating at low speeds, the belt 332engages the slide sleeve 364. At low operational speeds of the engine10, the inner and outer halves 234, 326 of the drive pulley 322 do notclamp the belt between them. In fact, as illustrated in FIGS. 21 and 24,while the belt 332 is shown as abutting the belt engagement surface 336,there is a gap 372 at least between the belt and the inner half 234 ofthe drive pulley 322. Preferably, a gap also exists between the belt 332and the belt engagement surface 336. Accordingly, the slide sleeve 364is permitted to float on the underlying shaft 374 while the inner andouter halves 234, 326 of the drive pulley 322 rotate. More accurately,the shaft 374 rotates beneath the slide sleeve 364. As a result, theslide sleeve 364 and belt 332 are stationary during low speed operationof the engine 10, especially during idle speed.

When the rotational speed of the engine 10 exceeds a predeterminedthreshhold, the centrifugal weights 344 begin their outward swing,causing the outer half 326 of the drive pulley 322 to move toward theinner half 234, clamping the belt 332 between them. Once this occurs,torque from the engine 10 is transmitted to the driven pulley 324, whereit is transmitted to the wheels 18, 20.

The slide sleeve 364 permits the construction of a brake assembly 362,which may be engaged while the engine 10 is operating. Without the slidesleeve 364, torque from the engine 10 always would be transferred to theCVT 26. As a result, even if the engine 10 were operating at low speeds,the wheels 18, 20 would be encouraged to move and the AVT 16 would havea tendency to creep forward. With the slide sleeve 364, however, thebelt 332 does not transfer torque to the driven pulley 324, which meansthat the ATV 16 does not have a tendency to creep forward. As a result,the brake assembly 362 maybe engaged even while the engine 10 isoperating without fear of damage to the brake assembly 362.

So that the slide sleeve 364 also permits the CVT 26 to operate as aRTT, at least one pin 366, but preferably two or more pins 366, biasedoutwardly with a spring 376, projects from the shaft 374. Preferably,the pin 366 is hexagonally shaped but, as would be understood by thoseskilled in the art, the pin 366 could take any suitable shape. Inparticular the pin 366 could be replaced by a ball bearing disposed atthe top of the spring 376 so that it engages the inside of the slidesleeve 364.

Various views of the slide sleeve 364 are provided in FIGS. 25-27. Theseviews highlight the construction of the inner surface 378 of the slidesleeve 364, which includes at least one helically-shaped groove 380. Asillustrated in FIG. 26, three helically shaped grooves 380 arepreferably provided. One pin 366 preferably engages each groove 380.

The grooves are shaped to be shallow 382 in one direction and steep 384in another. The shallow sides 382 permit the pins 366 to slide over themwhen the engine 10 operates in the forward direction (positive torque).In other words, the shallow sides 382 of the grooves do not engage thepins 366. Moreover, the shallow sides 382 are shallow enough that thepins 366 generate little noise as they move over the grooves 380 duringforward operation of the engine 10.

The steep portions 384 of the grooves 380 permit the slide sleeve 364 tooperate as a RTT. In particular, if the AVT 16 is pushed forward so thatthe torque from the wheels 18, 20 is applied to the slide sleeve 364,the pins 366 will engage the groove 380, hold the slide sleeve 364stationary with respect to the shaft 374, and, thereby, transfer thetorque from the wheels 18, 20 to the engine 10. The shallower guidepaths can result in less noise from the pins moving over the guidepaths. The number and width of the guide paths can be varied as desired.

In addition, on one side, the slide sleeve 364 includes an annular,flange-shaped end 386 with an external radius larger than that of theremaining portion of the slide sleeve 364. This annular flange 386serves as catch flank for the elastic belt 332 so as to press it againstthe outer part 326 of the drive pulley 322 during the RRT-mode, which isillustrated in FIG. 24. The axial pressing effect is achieved bycoaction with the spiral grooves 380 and the pins 366. The flange 386preferably has a minimum height so as to not ride under the belt 332. Inaddition, the flange 386 preferably has a maximum height so as to notoverly reduce the effective belt engagement surface 334 of the drivepulley inner half 234.

As illustrated in FIGS. 20 and 24, the belt engagement surface 334 ofthe drive pulley inner half 234 includes a recess 335 that accommodatesthe flange 386. As such, there is a smooth transition as the belt 332moves outwardly within the drive pulley 322 from the slide sleeve 364.

The drive spring 342 serves one additional function with respect to theslide sleeve 364. On one hand, it serves to enable the starting positionof the drive pulley 322 when the engine 10 stands still as illustratedin FIG. 21. On the other hand, it functions to return the catch flank386 of the slide sleeve 364 into its starting position during normaloperation. This prevents the flange 386 from catching the belt 332 as itmoves down the drive pulley 322 when the engine speed decreases.

If the engine 10 is started by thrust and the belt 332 is pressed by theflange 386 against the outer pulley part 326 of the drive pulley 322, aconnection is made between the pulley halves 234, 326 and the elasticbelt 332 via the flank sides of the belt 332. The minimum coupling speedcan be designed into the CVT 26 so that the belt 332 must move at asufficient speed before the RTT mode will engage. Once engaged, as thespeed of the belt 332 (or number of revolutions of the drive pulley 322)increases, the centrifugal weights 344 will move outwardly. This willcause the drive pulley outer plate member 348 to move inwardly, clampingthe belt 332 between the belt engaging surfaces 334, 336.

During normal operation (e.g., non-RTT operation), it is preferred tomaintain as constant a tension in the elastic belt 332 as possible,because a constant tension will ensure satisfactory torque transmissionfrom the drive pulley 322 to the driven pulley 324. The driven pulley324 assures that the tension on the belt 332 remains constant. The innerhalf 328 of the driven pulley 324 is instrumental here.

The inner half 328 of the driven pulley 324 includes a guide member 388.The guide member 388 is illustrated in greater detail in FIG. 28. Theguide member 388 engages with a toothed wheel 390, which is fixedlyconnected to the driven-side axle 392. The guide member 388 and theinner half 328 of the driven pulley 324 are mutually engaged viaprojections 394. As illustrated in FIG. 28, three two-sided projections394 are preferred for guide member 388. However, as would be understoodby those skilled in the art, any number of projections 394 may beemployed. The projections 394 enable the guide member 388 and the innerhalf 328 of the driven pulley 324 to slide into each other and to slideapart from one another during operation.

Each of the projections 394 include a normal operation ramp 396 and aRTT operation ramp 398, which are engaged alternatively depending on theoperation of the CVT 26. The shapes of the ramps 396, 398 are designedfor each of the two operation types. In particular, the normal operationramps 396 are given a steep slope. The RTT ramps 398, however, are notgiven as steep a slope as the normal operation ramps 396. The outer ends(the flank region) of the projections 394 are designed to be flat, whichhelps to maintain the tension in the belt 332 approximately constant,e.g., when the vehicle is pushed or towed to start the engine 10 (RTTmode of operation). The flat portions 400 of the RTT ramps 398 increasethe force applied by the inner half 328 to the outer half 330, therebycompensating for the lack of force (or reduced force) applied by theexpanded driven spring 360 and the inactive centrifugal weights 344. Theflat portion 400 of the projections 394 preferably are provided withapproximately a 15° inclination.

During RTT operation of the CVT 26, the RTT ramps engage correspondingsurfaces on the interior of the inner half of the driven pulley 324,which are illustrated in FIG. 31. The gearing characteristics of theguide member 388 may be determined by the shape and slope of thecorresponding ramps 396, 398.

The guide member 388 preferably is made of a synthetic material. Besidesproviding a light-weight construction, a synthetic material also offersa great acoustic advantage since the noise development at the onset ofdriving, when the two ramps collide, is greatly reduced as compared toother materials. Preferably, the guide member 388 is made fromfiberglass. For example, it is contemplated that the guide member 388may be constructed from a carbon fiber material. Of course, as would beappreciated by those skilled in the art, other materials may be selectedtherefor without deviating from the scope of the present invention.

The outer half 330 of the driven pulley 324 is operationally coupled tothe inner half 328 through a connector 402, which is illustrated ingreater detail in FIG. 29. The connector, which is preferably made of amaterial that is at least 2% teflon® (polytetrafluoroethylene), includesribbed sections 404 connected by non-ribbed sections 406. The ribbedsections 406 engage similarly-shaped indentations 408 on the hub 410 ofthe inner half 328 of the driven pulley 324, as shown in FIG. 30. Whilenot shown, the ribbed sections 404 also engage similar indentations onthe outer half 330 of the driven pulley 324.

The outer and inner halves 330, 328 of the driven pulley 324 arejournaled on the pulley shaft 401 by both slide bearings 403 and ballbearings 405. Thus, they are not rigidly coupled to the shaft 401. Thetransmission of torque from the pulley shaft 401 to the driven pulley324 is accomplished solely by the guide member 388 and its associatedramps 396, 398. In contrast to CVT constructions known in the prior art,where the outer half of the driven pulley is rigidly fixed to the drivenpulley shaft, the outer half 330 and the pulley shaft 401 in the CVT 26of the present invention are decoupled. The decoupling of these twoelements eliminates or at least greatly reduces torsional vibrationswhich are otherwise caused by the inertia of the outer half of thedriven pulley. Furthermore, the connector 402 prevents relative movementbetween the inner and outer halves 328, 330 of the driven pulley 324,which reduces considerably slip and friction between the belt 332 andthe pulley halves 328, 330.

As illustrated in FIG. 31, the inner surface of the inner half 328 ofthe driven pulley 324 includes radial ribs 410 and circumferential ribs412. These ribs 410, 412 increase to structural strength of the half 328to prevent micro-cracks from forming during operation.

FIG. 32 illustrates on alternative embodiment of the centrifugal weights344. In FIG. 32, a centrifugal weight 414 is illustrated. Thecentrifugal weight 414 includes a hole 416 at one end that may bepivotally connected to the drive pulley roller member 354. Thecentrifugal weight 414 is essentially the same as the centrifugal weight344, except that the centrifugal weight 414 includes a plurality ofindentations 418 along its outer surface 420, inward from the stop 422.The indentations 418 are designed to delay the advancement of thecentrifugal weights 414 as they pivot outwardly against the rollers 352.When provided with the indentations 418, the centrifugal weights 414behave such that the operator feels like the ATV 16 is changing gears,like a conventionally-geared ATV.

Specifically, the wave-type geometry on the outer surfaces 420 of thecentrifugal weights 414 defines the indentations 418. The rollers 352will come to rest in one of the wave indentations 418 only within acertain range of engine speeds. Only when a certain engine speed limitis exceeded will the rollers 352 advance to the next indentation 418,thus, progressing in a step-wise fashion to simulate changes from alower gear to a higher one.

Alternatively, while specific outer surfaces 350, 420 are illustratedfor the centrifugal weights 344, 414, there are many alternative shapesthat may be applied. It is expected that different shapes will influencethe operation of the CVT 26 to change the operational characteristics ofthe ATV 16. Specifically, the geometry of the outer surface 350, 420conceivably could offer more/less aggressive operational characteristicsfor the ATV 16. In addition, the centrifugal weights 344, 414 do not allneed to be the same shape. It is envisioned that weights 344, 414 ofdiffering shapes could be positioned about the periphery of the drivegear 322 to alter or control the operational characteristics of the ATV16.

FIG. 33 illustrates an alternative embodiment of a driven pulley, apneumatically-actuated driven pulley 424. In the pneumatic driven pulley424, movement between the inner half 426 and the outer half 428 of thepulley 424 is actuated pneumatically, preferably with vacuum pressurefrom the crankcase 74 of the engine 10. In this embodiment, guide member388 may be eliminated altogether. Alternatively, guide member 388 may beprovided, so that the driven pulley 424 may continue to operate evenupon loss of pneumatic control.

So that the pneumatically driven pullley 424 may operate, a number ofseals 430, 432, 434, 436, 438, 440 are provided between the inner half426 and the outer half 428. The application of vacuum to the innerchamber 442 via the vacuum connector 446 draws the two halves 426, 428together to provide a tight clamping force on the belt 332 positionedtherebetween. The vacuum can be supplied by a pneumatic coupling (notshown) mounted to the CVT cover 28 that allows vacuum to be selectivelysupplied from the engine 10 (or other vacuum source, such as a vacuumpump) to chamber 442 via connector 446.

It is expected that this type of driven pulley 424 should be especiallyeffective for providing engine braking to the ATV 16. In particular,upon deceleration of the engine 10, the throttle will be closed,resulting in a high vacuum in the engine 10, which will provide a strongclamping force between the two halves 426, 428. As a result, the belt332 will be clamped more tightly between the pulley halves 426, 428 ascompared with other driven gears for CVTs. This means that enginebraking may be applied effectively from the engine 10 to the vehicle 16.Alternatively, a pressure chamber could be positioned on the oppositeside of pulley half 426 such that a pressure source (rather than avacuum source) could be used to clamp the pulley halves 426, 428together. Furthermore, it is contemplated that a vacuum valve may beprovided to control vacuum pressure. If provided, it is contemplatedthat the vacuum valve could be a solenoid whose operation is controlledby the electronic control unit (or “ECU”) of the engine 10.

11. The Gear Shift

FIGS. 7 and 34-38 illustrate a further feature of the engine 10 of thepresent invention, a gear shift mechanism 448, which provides athree-step gear shift. The gear shift 448 includes a toothed wheel gear450 having five possible positions: high, low, neutral, reverse andparking. Via a selector shaft 452, which is non-rotationally connectedto the toothed gear 450, transmission of the gear positions to a controlshaft 454 is effected.

As illustrated in FIG. 37, the surface of the control shaft 454 includestwo grooves 456, 458. The grooves correspond to toothed wheels 460, 462,depending upon the position (i.e. rotation) of the control shaft 454,which is selected via selector forks 91, 93 to move into the correctposition.

In the “low” position, the selector fork 464 and the corresponding geartoothed wheel 462 are positioned on the left-hand side of the inputshaft. Te toothed wheel 470 is displaced with the selector fork 466towards the left-hand side on the driven shaft to effect anon-rotational connection with the toothed wheel 468. In the “high”position, the left-hand selecting fork 464 is displaced towards theright. As a result, the toothed wheel 460 is displaced toward the rightso that it non-rotationally engages with a toothed wheel 462, whichmeshes with the toothed wheel 470 on the output shaft. In the “reverse”position, the right-hand selecting fork 466 and the toothed wheel 470are displaced on the output shaft towards the right-hand side.Accordingly, toothed wheel 472 effects a meshing engagement with toothedwheel 474. In the “parking” position, the two selector forks 464, 466remain in the same position as in the “neutral” position. However, afork 476 with a three-toothed segment, which is forcibly guided via afork pin 478 engaged with a groove 480 on the toothed segment 482, ispivoted towards the gear 470. FIGS. 38 and 39 are illustrative of thisoperation. In particular, FIG. 38 shows the fork 476 disengaged from thegear 470 when the vehicle is not parked. FIG. 39 shows the fork 476engaged with the gear 470 in the park position to lock the gear 470 andprevent movement of the vehicle. The teeth on the fork 476 and the teethon the gear 470 preferably are self-locking, as would be understood bythose skilled in the art.

Three sensors are provided to detect the position of the control shaft454. Between the control shaft 454 and the sensors, an index disk 484 isinterposed, which interacts with the index lever. The index disk 484 andenables an exact positioning of the selector forks 464, 466 bypermitting them to mesh with the appropriate position on the selectorshaft 452. The index disk 484 also enables identification of thepositions “neutral,” “reverse,” and “parking” via an electric connectionto ground.

12. The Timing Chain Tensioner

As illustrated in FIG. 4, the timing control chain 54 is provided with amechanical timing chain tensioner 486, which is positioned in thecylinder block 132. While a mechanical timing chain tensioner 486 ispreferred, the tensioner 486 alternatively could be hydraulically orelectrically controlled, as would be understood by those skilled in theart.

13. The Control Device

The engine 10 is equipped with a combined battery/magneto ignition (notshown). The advantages of this installation is that the engine 10 isexpected to operate even if the battery fails. The ignition includes a400 W generator, which is provided with a start/stop switch.

For engine speed measurement and ignition timing, a sensor is attachedto the magnet wheel 42. Furthermore, vehicle speed measurement isprovided by a Hall sensor on the bevel wheel gear. In addition, anengine speed delimiter is provided. A delimiter is provided, which canbe programmed to a maximum speed of 15-20 km/h (return gear) and 0-139km/h (forward gear).

Attempts are made to obtain as “soft” a revolution delimitation aspossible via a sparking angle control (sparking instant control). Thesparking angle control is effected via a programable ignition time anglecontrol. This can be supplemented with the optional omission ofingitions. The throttle position in the carburettor (suction carburettorwith throttle flap flat slide for the nozzle needle) may be monitoredvia a further sensor. Finally, an oil pressure control is provided whichtriggers the engine speed delimiter or even causes the omission ofignitions when the oil pressure falls under a critical level (≈0.3-0.6atm).

14. The ATV Layout

The disposition of the engine 10 on the frame 17 of the ATV 16 is alsoan aspect of the present invention. The particular arrangement of theengine 10 on the frame 17 is illustrated in FIG. 3.

In the present invention, the engine 10 is positioned on the frame 17 ofthe ATV 16 such that the cylinder 34 is located at the rear of theengine 10. As such, the CVT 26 preferably is disposed on the left sideof the ATV 16, the right and left sides of the ATV 16 being defined bythe ATV's forward travel direction. With this positioning, the outputshaft 30 of the engine 10 preferably is disposed on the right side ofthe centerline 488 of the ATV 16. In addition, with the engine 10positioned on the frame in this manner, the crankshaft 12 and drivepulley shaft 374 are positioned behind the driven pulley shaft 401.

The centerline 14 of the engine 10, which is defined by the axis of thecylinder 34, preferably is disposed distance b from the centerline 488of the ATV 16, as illustrated in FIG. 3. With this arrangement, thecenterline 490 of the CVT 26, which is defined by the line along whichthe belt 332 travels between the drive pulley 322 and the driven pulley324, is disposed distance d from the centerline 488 of the CVT. Asindicated above, the centerline 14 of the engine 10 and the centerline490 of the CVT 26 are both disposed on the left side of the centerline488 of the ATV 16. The centerline 492 of the output shaft 30 preferablyis disposed distance c from the centerline 488 toward the right side ofthe ATV 16. As indicated in FIG. 3, the centerline 488 of the ATV 16 isdefined such that the distance from the centerline 488 to the frontwheels is measured by substantially the same distance a.

With this arrangement, the output shaft 30 is arranged on one side ofthe centerline 488 of the ATV 16 while the centerline 14 of the engine10 and the centerline 490 of the CVT 26 are arranged on the other side.This provides for a more balanced positioning of the engine 10 on theframe 17 of the ATV 16 of the present invention. As mentioned above,however, the engine 10 may be reversed in it orientation on the frame 17of the ATV 16. If so, the relationaship between the various componentsof the engine 10 and ATV 16 will remain the same but the orientationwill, naturally, be opposite to that described above.

While the preferred embodiments of the present invention have beendescribed above, the present invention is not meant to be limited solelyto those embodiments. Instead, the present inventionis meant toencompass any and all equivalents to the embodiments described above, tothe extent consistent with the forwgoing description and the appendedclaims.

What is claimed is:
 1. A drive pulley for a continuously variable transmission, comprising: a shaft adapted for operative connection to an engine crankshaft; an inner half rotatably disposed on the shaft, the inner half having a belt engagement surface associated therewith adapted to engage a first side of a belt; an outer half rotatably disposed on the shaft, the outer half having a belt engagement surface associated therewith adapted to engage a second side of the belt; a slide sleeve disposed on the shaft adapted to engage an inner side of the belt, wherein the slide sleeve has at least one groove disposed on an inner surface of the slide sleeve; at least one pin extending from the shaft; and a spring biasing the inner half and the outer half apart from one another, wherein the slide sleeve freely rotates with respect to the shaft when the belt is engaged thereby and the belt either is stationary or travels in a first direction, wherein the slide sleeve is fixed with respect to the shaft when the belt travels in a second direction, opposite to the first direction, and wherein the at least one pin being biased to engage the at least one groove when the belt travels in the second direction.
 2. The drive pulley of claim 1, wherein: the at least one groove comprises three grooves spirally disposed on the inner surface of the slide sleeve and the at least one pin comprises three pins, one each disposed in connection with each groove.
 3. The drive pulley of claim 2, wherein: the grooves each comprise a first surface and a second surface, the second surface being angled more steeply than the first surface, the first surface permits the pins to slide therefrom when the belt engages the slide surface and the belt either is stationary or travels in the first direction, and the second surface permits the pins to engage therewith when the belt travels in the second direction.
 4. The drive pulley of claim 1, wherein: the groove comprises a first surface and a second surface, the second surface being angled more steeply than the first surface, the first surface permits the pin to slide therefrom when the belt engages the slide surface and the belt either is stationary or travels in the first direction, and the second surface permits the pin to engage therewith when the belt travels in the second direction.
 5. The drive pulley of claim 1, wherein the slide sleeve further comprises: an annular flange extending outwardly from an outer surface on one end, wherein the annular flange engages at least a portion of the first side of the belt when the belt engages the slide sleeve and travels in the second direction.
 6. The drive pulley of claim 1, further comprising: at least one antifriction bearing journaling the slide sleeve to the shaft.
 7. The drive pulley of claim 1, wherein: the outer half further comprises at least one centrifugal weight pivotally mounted thereto so that the centrifugal weight swings outwardly upon application of a centrifugal force, applies a pressing force against an associated roller disposed on the outer half, and causes the outer half belt engaging surface to move towards the inner half belt engaging surface, sandwiching the belt therebetween.
 8. The drive pulley of claim 7, wherein: the at least one centrifugal weight is provided with a plurality of indentations on its outer surface to engage the roller at specific engine speeds, momentarily delay the advancement of the outer half belt engagement surface toward the inner half belt engaging surface, and provide an operation comparable to a traditional geared transmission.
 9. A driven pulley for a continuously variable transmission, comprising: a shaft adapted for operative connection to an output shaft of the continuously variable transmission; an inner half rotatably disposed on the shaft, the inner half having a belt engagement surface associated therewith adapted to engage a first side of a belt; an outer half rotatably disposed on the shaft, the outer half having a belt engagement surface associated therewith adapted to engage a second side of the belt; a spring biasing the inner half and the outer half together with one another; and a connector rotatably coupling the inner half with the outer half, wherein the connector is disposed between the inner half and the outer half, wherein both of the inner half and the outer half can transmit torque to the shaft through one of the inner half and the outer half.
 10. The driven pulley of claim 9, wherein: the connector comprises a ring having at least one ribbed portion and at least one non-ribbed portion, and at least one of the inner half and the outer half comprise at least one ridged section adapted to engage the at least one ribbed portion of the connector.
 11. The driven pulley of claim 10, wherein: the at least one ribbed portion comprises three ribbed portions, and the at least one ridge section comprises three ribbed sections.
 12. The driven pulley of claim 9, further comprising: a toothed wheel fixedly connected to the shaft; and a guide member operatively connected to the toothed wheel comprising at least one projection adapted to mate with at least one indentation on the inner half.
 13. The driven pulley of claim 12, wherein: the guide member comprises a synthetic material.
 14. The driven pulley of claim 13, wherein: the guide member comprises fiberglass.
 15. The driven pulley of claim 13, wherein: the guide member comprises carbon fiber.
 16. The driven pulley of claim 12, wherein the at least one projection comprises: a first ramp with at least one first slope; and a second ramp with at least one second slope that is less than the at least one first slope, wherein the first ramp is adapted to engage the inner half during a normal mode of operation of the driven pulley, and wherein the second ramp is adapted to engage the inner half during a reverse torque transmission mode of operation of the driven pulley.
 17. A continuously variable transmission, comprising: a drive pulley adapted to connect to a crankshaft of an engine, the drive pulley comprising a drive pulley inner half rotatably disposed on the shaft, the drive pulley inner half having a belt engagement surface associated therewith adapted to engage a first side of a belt, a drive pulley outer half rotatably disposed on the shaft, the drive pulley outer half having a belt engagement surface associated therewith adapted to engage a second side of the belt, a slide sleeve disposed on the shaft adapted to engage an inner side of the belt, wherein the slide sleeve has at least one groove disposed on an inner surface of the slide sleeve, at least one pin extending from the shaft, and a spring biasing the drive pulley inner half and the drive pulley outer half apart from one another, wherein the slide sleeve freely rotates with respect to the shaft when the belt is engaged thereby and the belt either is stationary or travels in a first direction, and wherein the slide sleeve is fixed with respect to the shaft when the belt travels in a second direction, opposite to the first direction, and wherein the at least one the pin being biased to engage the at least one groove when the belt travels in the second direction; and a driven pulley adapted to connect to an output shaft of the continuously variable transmission, the driven pulley comprising a driven pulley inner half disposed on the shaft, the driven pulley inner half having a belt engagement surface associated therewith adapted to engage a first side of a belt, a driven pulley outer half disposed on the shaft, the driven pulley outer half having a belt engagement surface associated therewith adapted to engage a second side of the belt, a spring biasing the driven pulley inner half and the driven pulley outer half together with one another, and a connector rotatably coupling the driven pulley inner half with the driven pulley outer half, wherein the connector is disposed between the driven pulley inner half and the driven pulley outer half.
 18. The continuously variable transmission of claim 17, wherein: the at least one groove comprises three grooves spirally disposed on the inner surface of the slide sleeve and the at least one pin comprises three pins, one each disposed in connection with each groove.
 19. The continuously variable transmission of claim 18, wherein: the grooves each comprise a first surface and a second surface, the second surface being angled more steeply than the first surface, the first surface permits the pins to slide therefrom when the belt engages the slide surface and the belt either is stationary or travels in the first direction, and the second surface permits the pins to engage therewith when the belt travels in the second direction.
 20. The continuously variable transmission of claim 17, wherein: the groove comprises a first surface and a second surface, the second surface being angled more steeply than the first surface, the first surface permits the pin to slide therefrom when the belt engages the slide surface and the belt either is stationary or travels in the first direction, and the second surface permits the pin to engage therewith when the belt travels in the second direction.
 21. The continuously variable transmission of claim 17, wherein the slide sleeve further comprises: an annular flange extending outwardly from an outer surface on one end, wherein the annular flange engages at least a portion of the first side of the belt when the belt engages the slide sleeve and travels in the second direction.
 22. The continuously variable transmission of claim 17, further comprising: at least one antifriction bearing journaling the slide sleeve to the shaft.
 23. The continuously variable transmission of claim 17, wherein: the outer half further comprises at least one centrifugal weight pivotally mounted thereto so that the centrifugal weight swings outwardly upon application of a centrifugal force, applies a pressing force against an associated roller disposed on the outer half, and causes the outer half belt engaging surface to move towards the inner half belt engaging surface, sandwiching the belt therebetween.
 24. The continuously variable transmission of claim 17, wherein: the at least on centrifugal weight is provided with a plurality of indentations on its outer surface to engage the roller at specific engine speeds, momentarily delay the advancement of the outer half belt engagement surface toward the inner half belt engaging surface, and provide an operation comparable to a traditional geared transmission.
 25. The continuously variable transmission of claim 24, wherein: the connector comprises a ring having at Least one ribbed portion and at least one non-ribbed portion, and the driven pulley inner half and the driven pulley outer half both comprise at least one ridged section adapted to engage the at least one ribbed portion of the connector.
 26. The continuously variable transmission of claim 24, further comprising: a toothed wheel fixedly connected to the shaft; and a guide member operatively connected to the toothed wheel comprising at least one projection adapted to mate with at least one indentation on the inner half.
 27. The continuously variable transmission of claim 26, wherein the at least one projection comprises: a first ramp with at least one first slope; and a second ramp with at least one second slope that is less than the at least one first slope, wherein the first ramp is adapted to engage the inner half during a normal mode of operation of the driven pulley, and wherein the second ramp is adapted to engage the inner half during a reverse torque transmission mode of operation of the driven pulley.
 28. The continuously variable transmission of claim 27, wherein: the guide member comprises a synthetic material.
 29. The continuously variable transmission of claim 28, wherein: the guide member comprises fiberglass.
 30. The continuously variable transmission of claim 28, wherein: the guide member comprises carbon fiber. 